Method of producing electrical resistance units



Sept. 19, 1939. w 11 sw R-rz ET AL 2,173,186

METHOD OF PRODUCING ELECTRICAL RESISTANCE UNITS I I II n c Iiiiffliiwiii iili'iiil ii fi 5 7 35 39 .465 .50 5 t 77 v b'u '41 1:

Patented Sept. 19, 1939 UNITED s'mrss PATENT oFFicE METHOD OF PRODUCINGELECTRICAL RESKSTANCE UNITS Original application August 26, 1929, SerialNo.

388,359. Divided and this application August 30, 1934, Serial No.742,118 r V 3 Claims.

This invention relates particularly to the formation of electricalresistance units that are capable of replacement and is especiallydirected to the method of manufacture of said units, and is a divisionof our prior application Serial No. 388,359, filed August 26, 1929 nowU. S. Patent No. 1,972,411.

This invention comprehends the method by which resistance units may bemanufactured in gangs and includes novel means for embedding theterminals therein.

Specifically stated, the form of my invention as hereinafter set forthcomprises resistance units which are produced in strip or gang formationand readily separated from such strip by bending back and forth along arestricted groove or furrow. The metallic terminals, being in suitablyperforated sheet strip form, are placed in a mold and plastic resistancematerial subjected to pressur in said mold is caused to be embedded inthe perforations provided therefor, said strip being perforated in theline of separation of the individual units so as to facilitate thebreaking part of said units from the gang thus formed.

This invention also includes all of the various novel features ofconstruction and arrangement as hereinafter more definitely specified.

In the accompanying drawing, Fig. 1 is a plan View illustrating a sheetmetal strip of connected contact members adapted to be molded into thegang resistance elements; Fig. 2 is a fragmentary plan View of the baseflask or lower section and coping of the mold showing the resistanceunits molded in gang formation; Fig. 3 is a fragmentary transversevertical sectional view of the assembled mold taken transversely throughsaid units on the line 33 in Fig. 2; Fig. 4 is a fragmentary transversevertical sectional view of the assembled mold taken longitudinally ofthe units therein on their line of separation as indicated by the linei4 in Fig. 2; and Fig. 5 is a perspective view of a fragment of thelower former bar of the mold.

The new resistance unit has made possible a unique and economical methodof manufacture. Under this method the lugs are punched from sheet metal,preferably copper tinned on both sides, the punching being done in suchmanner that the lugs remain connected together in strip form as shown inFig. 1; in other words, the lugs are produced in a series, the stripwhich units the lugs being punched out to afford the apertures 3 and 5,so that the individual adjacent lugs are connected only by narrow webs32 and 33 of metal left between them, whereby the units may be readilyseparated by bending and causing fracture of said webs. The strip may beof any desired length and therefore may contain as many lugs as thereare units to be molded. Applicant has found that thirty units can beconveniently handled at a single operation.

The portion of the strip of lugs above the dotand-dash line in Fig. 1 isheld in that part of the mold which may be termed the insert or lug vholder, while that portion of the'strip below line,

extends into the hollow portion of the mold in which the resistancematerial is molded. This material is thus molded into intimate contactwith all that portion of the strip below said dotand-dash line and notonly embraces the inner margin of said strip but is forced through theperforations 3 and '5 so that the materialon one side of the strip isunited to that on the other side, thus securely locking the strip in themolded material to form an integral structure.

The mold, as illustrated in Figs. 2, 3, 4 and 5, is preferably made ofhardened steel and comprises the bottom plate 35, the side and endpieces 36 and 3? respectively, which may be best attached to the bottomplate 35, the filler or holding blocks 33 and 39 between which the lugportion of the lug strips, as shown in Figs. 2 and 3, may be inserted,the position of said lug strips being determined by the stop pins 40 and4|.

Said mold is so constructed as to produce a multiple im pression, beingprovided with the forming blocks t2 and 43 respectively havingwedge-shaped dividing ridges 45 and 46 which register in opposedrelation so that when the two halves of the mold are brought togetherunder pressure the moldable material is formed into individual unitswhich may either be taken from the mold with the lugs of the units stillconnected by a. thin web, which may be readily broken, or the mold maybe so constructed as to sever the said webs and deliver the unitsalready separated. It has been found in practice that best results areobtained by forcing the forming blocks together in the press topartially cut through the webs 32 and 33, thereby facilitating theseparation of the units.

The form of electrical resistance unit chosen for illustration in themold as shown in Fig. 2, has the margin of the sheet metal strip of lugsi5 being embedded in the upper ends of the elements I and the margin ofthe sheet metal strip of lugs I6 being embedded in the lower ends ofsaid elements.

This invention is advantageous in that] by means of the method ofproduction and distribution as above described substantial economies areeffected as compared with the methods heretofore employed, wherein eachindividual lug or insert had to be picked up and loaded into the mold.

It is desired that this invention be not limited to the precise detailsof construction and arrangement as herein set forth, as it is obviousthat various modifications may be made therein without departing fromthe essential features of this invention as defined in the appendedclaims.

Having thus described our invention, we claim:

1. The method of producing resistance units comprising a plastic bodyconnecting relatively spaced terminal members having relativelyseparable regions affording oppositely directed alined terminalcontacts, which consists in forming metallic strips with an indentededge, weakening the strips along the lines of indentation, mounting saidstrips with the terminal contacts of the respective strips joined inunitary relation in a common plane in relatively spaced relation in amold having movable members each provided with opposed antagonized edgedridges, introducing a plastic molding material into the mold cavity incontact with the opposing margins of said strips to form a connectingbody for said strips, and forcing together the relatively movable moldmembers with sufiicient force to form a plurality of parallel groovesupon the opposite faces of said body and strips in alinement with theindentations in the edges of said strips.

2. The method of producing resistance units comprising a plastic bodyconnecting relatively spaced terminal members each having relativelyseparable regions aifording oppositely directed alined terminalcontacts, which consists in forming metallic strips with an indentededge, perforating said strips at the regions of indentation, mountingsaid strips with the terminal contacts of the respective strips joinedin unitary relation in a common plane in relatively spaced relation in amold having relatively movable members each provided with opposedantagonized ridges, introducing a plastic molding material into the moldcavity in contact with the opposing margins of said strips to form aconnecting body for said strips and forcing together the relativelymovable mold members with sufficient force to form a plurality ofparallel grooves upon the opposite faces of said body and said strips inalinement with the indentations in the edges of said strips and acrossthe perforated regions.

3. The method of producing resistance units comprising a plastic bodyconnecting relatively spaced terminal members each having relativelyseparable regions affording opposed oppositely directed alined terminalcontacts, which consists in forming metallic strips having relativelyseparable regions, mounting said strips with the terminal contacts ofthe respective strips joined in unitary relation in a common plane inrelatively spaced relation in a mold having relatively movable memberseach provided with antagonized regions, introducing plastic moldingmaterial into the mold cavity in contact with the opposing margins ofsaid strips to form a connecting body for said strips and forcingtogether the relatively movable mold members with sufiicient force toform a plurality of parallel grooves upon the opposite faces of saidbody and strips between the relatively separable regions of said strips.

TORRENCE A. SWARTZ. WILMER P. UHLER.

